Adversing: 01622 699116
The queson of how much hot water is required for a project is a constant dilemma for designers, installers and end users. Too lile supply results in customer complaints, while over storage adversely aects the health of the system, leading to unnecessary expenditure.
indirect calorifiers, direct-fired appliances and plate heat
H
exchangers to meet the ever increasing demands for hot water in the commercial market. When supplying a traditional indirect HWS cylinder with an 80°C primary flow, the less dense secondary water rises to the top of the cylinder at the designed temperature. The de-stratification pump will return the hot water from the top of the cylinder back towards the base in an attempt to increase the temperature of the water at the bottom of the cylinder. Ultimately, however, this results in narrowing the t of the primary circuit therefore massively reducing a condensing boiler’s efficiency. One such method for supplying hot water during the summer was to have a dedicated summer boiler to indirectly provide LPHW to a calorifier. This was because there was no sense in operating an oversized boiler that was either operating at 100% or 0% to operate two showers
ADVERTISER’S ANNOUNCEMENT BSEE Hot stu from Mikrofill, indirectly
istorically, the UK has adopted
and a basin every hour during the summer period. In addition, legislation dictates that condensing boilers are often the go to product for the generation of LTHW in the commercial environment. As still the majority of new plant installations are retrofit projects, designers are immediately governed by the existing system’s t which is often not conducive to maximising condensing boiler efficiency.
The Extreme HWS loading cylinder
The Extreme combines a cleverly controlled PHE – designed to operate at a t of 30°C – and a storage cylinder, developed for modern commercial buildings. It has the advantages of both an instantaneous hot water heater and a storage system, creating perfect harmony between
condensing boilers and hot water cylinders.
Modern condensing boilers with turn down ratios of 10 > 1 sized to suit a building’s LPHW primary demand can easily
be prioritised to provide an indirect supply to an Extreme loading cylinder/s. A primary return of 50°C from the Extreme during the heating season would at least reduce the overall system
temperature returning back to the boilers. During the summer months the
condensing boilers efficiency is maximised for the majority of time it supplies primary water to the Extreme. The Extreme stainless steel PHE and cylinder packages are available in 200, 300 and 500 litre models and are capable of handling up to 120kW of primary input at a t of 30°C. What the Extreme does is to help remove some of the uncertainty frequently involved in the sizing of hot water storage.
The Extreme maximises condensing boiler efficiency as its PHE is designed to operate at a t of 30°C (80/50). It achieves 100% of its stored volume at the desired temperature and its instantaneous performance often allows a reduction in stored volume.
120kW input at 80ºC into a 500 litre Extreme will typically reach designed temperature (60ºC) in
around 12 minutes from a cold start. u10 minute peak
performance of 845 litres at 60°C = 1.41 l/s u1st hour performance of 2570 litres at 60°C = 0.7 l/s uContinuous performance of 2070 litres at 60°C = 0.57 l/s
Project example
Requirement of 20 showers each with a 60°C demand of 5.5 litres per minute u20 x 5.5 = 110 l/m maximum demand at 60°C uExtreme 500 (based on a 120kw input at 80°C) will produce 34.5 l/m at 60°C instantaneously uDemand of 110 l/m – 34.5 l/m = 75.5 l/m shortfall uExtreme 500 (stored volume) divided by 75.5 (shortfall) = 6.5 minutes
Conclusion
Twenty showers can operate simultaneously for a period of 6.5 minutes until the instantaneous supply will operate 30% of the showers thereafter.
To find out more about the operation or assistance in sizing an Extreme loading
uThe Extreme maximises condensing boiler eciency.
system, call 03452 606020 or visit:
www.mikrofill.com
NATURALLY INSPIRED EFFICIENCY
built for speed
· · ·
VISIT OUR WEBSITE:
www.bsee.co.uk
BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2018 9
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